| // Copyright 2016 The Android Open Source Project |
| // |
| // Licensed under the Apache License, Version 2.0 (the "License"); |
| // you may not use this file except in compliance with the License. |
| // You may obtain a copy of the License at |
| // |
| // http://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, software |
| // distributed under the License is distributed on an "AS IS" BASIS, |
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| // See the License for the specific language governing permissions and |
| // limitations under the License. |
| |
| #pragma once |
| |
| #include "android/base/Compiler.h" |
| #include "android/base/StringView.h" |
| #include "android/base/network/IpAddress.h" |
| |
| #include <vector> |
| |
| namespace android { |
| namespace base { |
| |
| // A convenience class to wrap the system's DNS resolver. |
| // |
| // Usage: |
| // Dns::AddressList list = Dns::resolveName("<server-name>"); |
| // if (list.empty()) { ... error ... } |
| // |
| class Dns { |
| public: |
| using AddressList = std::vector<IpAddress>; |
| |
| // Resolve name |server_name| into a list of IpAddress instances. |
| // Return an empty list on failure. |
| static AddressList resolveName(StringView server_name); |
| |
| // Return the list of DNS server addresses used by the system. |
| // This works by either parsing /etc/resolver.conf on Posix or |
| // calling the appropriate Win32 API. |
| static AddressList getSystemServerList(); |
| |
| // Abstract interface to a system resolver. |
| // Usage: |
| // 1) Use Resolver::get() to retrieve current instance. |
| // |
| // 2) Use Resolver::setForTesting() to inject custom version during |
| // unit-tests. |
| class Resolver { |
| public: |
| virtual ~Resolver() = default; |
| |
| // Parse |server_name| as a DNS server name or IP address and |
| // resolves it to a list of IpAddress instances. On success, return |
| // 0 and append results to |*out|. On failure, just return a negative |
| // errno code. |
| virtual int resolveName(StringView server_name, AddressList* out) = 0; |
| |
| // Return the list of DNS servers used by the system. On success, |
| // return 0 and append results to |*out|. On failure, just return |
| // a negative errno code. |
| virtual int getSystemServerList(AddressList* out) = 0; |
| |
| // Return current global resolver for the process. This can be |
| // altered with setForTesting(). Never returns nullptr. Creates |
| // a new instance lazily if necessary. |
| static Resolver* get(); |
| |
| // Change the process-global resolver. Return the old one, or |
| // nullptr. |resolver| can be nullptr, in which case a future |
| // call to get() will create a new system-level resolver |
| // (e.g. reparsing /etc/resolv.conf explicitly). |
| static Resolver* setForTesting(Resolver* resolver); |
| }; |
| }; |
| |
| } // namespace base |
| } // namespace android |